Liquid crystal displays (LCDs) use nematic liquid crystals sandwiched between glass plates to modulate light transmission through the display. When an electric field is applied to the liquid crystal layer by transparent ITO electrodes, the LC molecules, which are elongated in shape, align themselves parallel to the applied field and normal to the glass plates. In this state, polarized light travels through the LC layer without having its polarization state rotated. Because the LC module is placed between crossed polarizers, the display appears dark. In order for displays to allow light through when the applied field is off, the liquid crystal director on opposite sides of the glass chamber must be oriented 90° with respect to each other. In this situation, the polarization state of the light is rotated by 90° and exits parallel to the analyzer, thus making the display appear light. The orientation of the LC director at the surface of each glass plate is controlled by a so-called rubbing layer which is typically a polyimide layer that has undergone successive mechanical rubbing steps to create alignment of the polymer chains and mechanical grooving of the surface. This surface treatment induces the LCs to align parallel to the rubbing direction. In the current LCD manufacturing process, separate layers are used for the transparent ITO electrodes and the polyimide rubbing layers.
FIG. 1, generally at 100 shows a conventional passive matrix display. The conventional display in FIG. 1 includes a front plate and a back plate. The front plate includes glass plate 108 with a polarizing filter 110 at its exterior surface. Color filters 112, 114, and 116, red, green, and blue, respectively, are disposed on interior surface of the glass plate. The color filters 112, 114, and 116 are disposed adjacent one another. The filters are covered by transparent plate 118. Spaced apart transparent electrode 120 of ITO are disposed on the plate. These electrodes precisely overlay the color filters. Interior to transparent electrodes 120 is liquid crystal alignment layer 122.
The back plate consists of glass plate 102 that has polarizing filter 104 disposed at its exterior surface. The interior surface of glass plate 102 has spaced apart transparent electrodes 106 made from ITO disposed there. These electrodes are disposed perpendicular to electrodes 120 of the front plate. Interior to transparent electrodes 106 is alignment layer 107.
The two alignment layers are spaced apart by a spacer 124. Liquid crystals 126 are disposed in the spacer between the alignment layers.
There needs to be easy and efficient method to align the electrodes with the color filters.